Basic Physics-1

Basic Physics - Part I

 Sound waves are longitudinal waves.
 Sound waves cannot travel through vacuum.
 Acoustic is the subject dealing with the study of sound.
 Velocity of Sound is extreme in solid.
 The velocity of sound in air increases with increase in temperature.
 The velocity of sound in air is proportional to the square root of the absolute temperature.
 The sound of high pitch: Shrill
 The sound of low pitch: Sharp
 Hertz is the unit of frequency.
 Vibration of a string is a transverse motion.
 Stethoscope is based upon the principle of multiple reflection.
 Doppler effect describes the relationship between the pitch of sound and distance from the source of sound.
 Doppler effect: Describes to find binary stars,
 Sound signal is recorded as light signal on a cinema film.
 When sound waves enter from air into water they bend away from the normal.
 Light travels faster than sound.
 Whispering gallery; Gol Gumbaz.
 Uses of echoes: (1) Bats fly in the dark. (2) Detect the submarines under water.
 Echo: We hear original and then reflected sound.
 The obstacle should be at least 16.5 mts.
 The time interval between sound production and its echo is 1/10 of a second.
 Vibration of a string is transverse.
 Microphones convert sound into electric energy.
 Loud Speaker converts electric energy into mechanical energy and mechanical energy into sound energy.
 A sound of single frequency is called tone.
 Mach number: The ratio of the velocity of the body to the velocity of sound.
 Expression for simple harmonic motion: a Sin (Wt-Kn).
 The waves produced by the Sonometer is transverses stationary and polarized.
 Lissajous figures are very useful in comparing frequencies.
 The velocity of sound in gas is the square root of the adiabatic elasticity medium.
 The velocity of sound in air decrease with increase in pressure.
 The quality of tone depends upon the present.
 The frequencies of two vibrating systems equal it is called resonance.
 The velocity of sound in air is 332 meters/sec. 0 oC when the air is dry.
 Ultra sonics are detected by the thermal detector.
 Ultra sonic waves have frequencies higher than 20,000 Cycles per Sec.
 Infra sonic waves have the frequencies less than 20hz,
 A spherical liquid drop has a convex surface.
 Surface Tension: Soap bubble.
 The pressure inside a bubble is inversely proportional to its radius.
 Quincke's drop method is used for measuring surface tension and angle of contact for mercury in contact with glass.
 Cream separator: Centripetal force.
 Blotting paper: Capillary action.
 Adhesion: Force of attraction between unlike molecules.
 Cohension: Force of attraction between like molecules.
 Rocket: Conservation of momentum.
 Hygrometer: Instrument for measuring relative humidity.
 Tensimeter: Device for measuring vapour pressure.
 A falling in barometer: Storm.
 Ballory are filled with hydrogen.
 Sublimation: Vapourisation of a solid without first becoming a liquid.
 In pressure cooker the water boils at more than 100o C.
 Condensation: the change of vapour into liquid.
 Heat from the sun reaches the earth by way of radiation.
 Dry ice is solid carbondioxide.
 Pyrometer is used for measuring higher temp.
 When ice melts in a glass of water, the level of water in glass remains the same.
 If a ship enters into sea from the lake the level of the ship rises.
 S.I unit of heat is joule; in C.G.S system it is calorie.
 Hope's experiment proves the density of water is maximum at 4°C.
 The S.I unit of temperature is Kelvin.
 Thermostat used to maintain a constant temperature.
 Absolute zero: -273°C.
 Absolute zero: -460°F
 At -40° the Fahrenheit and Centigrade Scales are equal.
 At 574.25°F the Fahrenheit and Kelvin are equal.
 The temperature of human body is 36.9°C (fever:39°C).
 Latent heat of fusion of ice=336 x 103 J/kg.
 Regelation means refreezing.
 Thermometric scales: F = 9/5 C + 32 = 1.8C + 32, C = (5/9 F-32) = 0.56 F-18
 Laws of Reflection : (i) The angle of incidence is equal to the angle of reflection. (ii) The incident ray, reflected ray and normal to the surface lie in the same plane.
Parallel Mirrors:
 (i) The No of images formed when an object is· kept in between two plane mirror is infinite,
 (ii) 3 images are formed when the two mirrors are inclined and the angle between the two mirror is 90° (5 images when the.angle.is 60°, 7 images when the angle is 45°,11 images when the angle is 30°)
 (iii) The number of images formed (1) when the two mirros are inclained is equal to 1 = 360/1-1 is the angle between the mirrors
 (iv) The number of images formed in Kaleidoscope is 5 (angle between the mirror is 60°).
 (v) Kaleidoscope and periscope are based on the principle of multiple reflection.
 Short Sight –Myopia : Eye ball too long, Focal length too small, Objects nearer are Clearly seen,Focus in front of retina, Rectified with Concave lens
 Long Sight – Hyper Metropia : Eye ball too short, Focal length too long, Objects farer are Clearly seen, Focus behind the retina, Rectified with Convex lens
 Infrared rays are discussed by William Herschell,
 Wave length between 4X10-3 m and 7.5x 107m.
 Headed zirconium and heated tungsten carbide emits infra-red.
 Infrared: Used in the treatment of Thellmatic arthritis, Used in burglar alarms, Used in Photography (dew), The remote control (TV, VCR) sends commands in the form of infrared rays.
 Ultra-violet rays are discovered by Ritter.
 Wave length between 3900 X 10-lOm and 130.x 10-lOm.
 Source-Sun and Moon: Used in Forensic science lab, Ultra-violet radiations helps for the preparation of vitamin D, Used in the treatment of bone diseases and tumors. Used for sterilizing the air in operation theatres and laboratories.
 Laser: Light amplification by stimulated emissions of Radiation.
 The laser light is coherent monochromatic and extremely intense.
 The laser beam does not diverge.
 Light is a form of Energy.
 Light particles are known as photons.
 Light waves are electromagnetic.
 Velocity of the light: 3 x 108 m/sec.
 Corpuscle theory of light: Sir Issac Newton.
 Sky is blue due to Blue light is scattered the most by small particles of atmosphere.
 Bats fly in the dark: Ultra sonics.
 Velocity of light: Poucaulf's rotating mirror method.
 Energy of photons: E=hr where 'h' is the Planck's constant
(h =6.625 x10-34joules/sec)and r is the frequency of electromagnetic radiation.
 Rainbow formed due to: Dispersion.
 If a green colour leaf is seen in red light it will appear as black.
 Light travels fast in quarts.
 If a disc which has the pure spectral colours painted on it in proper proportion is rotated rapidly, it produces, white light.
 The distance between the projector and the screen, in a cinema theatre is increased by 1% the intensity of illumination is decreased by 2%.